Add workaround for inserting into addr2insn mapping

1 files changed, 8 insertions, 1 deletions

diff --git a/ujit_compile.c b/ujit_compile.c
index bfe75d1b7b..5980df59f5 100644
--- a/ujit_compile.c
+++ b/ujit_compile.c
@@ -64,7 +64,14 @@ addr2insn_bookkeeping(void *code_ptr, int insn)
     const void * const translated_address = table[insn];
     st_data_t encoded_insn_data;
     if (st_lookup(rb_encoded_insn_data, (st_data_t)translated_address, &encoded_insn_data)) {
-        st_insert(rb_encoded_insn_data, (st_data_t)code_ptr, encoded_insn_data);
+        // This is a roundabout way of doing an insert. Doing a plain insert can cause GC
+        // while inserting. While inserting, the table is in an inconsistent state and the
+        // GC can do a lookup in the table.
+        st_table *new_table = st_copy(rb_encoded_insn_data);
+        st_table *old_table = rb_encoded_insn_data;
+        st_insert(new_table, (st_data_t)code_ptr, encoded_insn_data);
+        rb_encoded_insn_data = new_table;
+        st_free_table(old_table);
     }
     else {
         rb_bug("ujit: failed to find info for original instruction while dealing with addr2insn");